FIELD OF THE INVENTION
The present invention relates to carboxylic acid derivatives. More specifically, the present invention relates to carboxylic acid derivatives having retinoic acid type pharmacological activities.
Retinoic acid (Vitamin A acid) is considered to be an active metabolite of Vitamin A. This compound has extremely important pharmacological activity for the maintenance of life. For instance, it induces differentiation on embryonic immature cells by which mature cells having characterized functions are produced. It also accelerates the proliferation of cells. From a clinical standpoint, retinoic acid is found to be useful for the treatment of avitaminosis of Vitamin A, epithelial hyperkeratosis, leukemia, and certain types of cancer. Various derivatives of Vitamin A prepared to date, such as the benzoic acid derivatives disclosed in Japanese Patent Unexamined Publication Nos. 61-22047 and 61-76440, are found to have such pharmcological activities. These compounds, including retinoic acid, which exhibit retinoic acid-type pharmacological activities are referred to as retinoids. However, all of the presently known retinoids are benzoic acid-type derivatives like those disclosed in the aforementioned publications, and no pyridine carboxylic acid-type retinoid is known to date.